How to Do a Surface Dive

Begin by floating or swimming face-down, with your arms extended out in front of you.

Sweep your arms back, bend your knees, tuck your legs toward your chest & bend your waist forward, so your head is pointing toward the bottom.

Straighten your legs and your body until you're upside-down & perpendicular to the surface, with your legs sticking up out of the water. Extend your arms towards the bottom & point your toes.

Once in this upside-down position, the weight of your legs in the air above will push you underwater.

Or,

Tread water in the deep end of the pool.

While treading water, kick your legs faster and take a breath of air. This will raise you up a little and provide momentum.

Stop kicking and keep your body straight.

Push the water up with your arms, then slide them back down. Repeat until you reach the bottom or run out of breath.. This is commonly called a "feet-first surface dive".